A light emitting diode (LED) is a semiconductor device that converts electricity into ultraviolet ray, visible ray or infrared ray by using characteristics of compound semiconductors. The LED is mainly used for home appliances, remote controllers and large-size electric signboards.
A high-brightness LED is used as a light source for a lighting device. Since the LED represents the superior energy efficiency and long life span, the replacement cost thereof may be reduced. In addition, the LED is strong against vibration and impact and it is not necessary to use toxic substances, such as Hg, so the LED substitutes for a glow lamp and a fluorescent lamp in terms of energy saving, environmental protection and cost reduction.
In addition, the LED may be advantageously used as a light source for a middle-size or large-size LCD TV and a monitor. When comparing with a cold cathode fluorescent lamp (CCFL) mainly used in a liquid crystal display (LCD), the LED represents superior color purity and low power consumption and can be fabricated in a small size, so various products equipped with the LED have been produced and studies for the LED have been actively performed.
Recently, a plurality of technologies are introduced to realize white light by employing a blue LED and using quantum dots to emit red and green light as a fluorescence substance. This is because the white light realized by using the quantum dots represents high brightness and superior color reproduction.
However, there still remains the requirement for researches and studies to reduce light loss and improve color uniformity when the LED is applied to a backlight unit.